ADU Garage Conversion Costs in San Jose (2026)

Converting an attached or detached garage into an ADU (Accessory Dwelling Unit) is one of the highest-ROI projects a San Jose homeowner can do in 2026. California SB 9 and San Jose's ADU-friendly rules have made permits faster — but real project costs still surprise most owners. Here's the honest breakdown.

For a 400–500 sq ft garage-to-ADU conversion in San Jose, most projects land between $130,000 and $220,000 all-in. The spread depends heavily on utilities, foundation condition, and finish level.

• Basic conversion (existing slab, minimal utility work): $130,000 – $160,000
• Standard conversion (new panel, HVAC, mid-range finishes): $160,000 – $200,000
• Premium conversion (full foundation upgrade, high-end finishes): $200,000 – $260,000+

Budget allocation on a typical San Jose garage conversion:

• Framing, insulation, drywall: 15–20%
• Electrical panel upgrade & rough-in: 10–15%
• Plumbing rough-in & sewer connection: 10–15%
• Kitchen & bathroom fixtures: 15–20%
• HVAC (mini-split typical): 5–8%
• Windows, doors, exterior: 8–12%
• Finishes (flooring, paint, cabinets): 15–20%
• Permits, plans, city fees: 5–8%

San Jose ADU permits typically clear in 60–90 days with a complete plan set. Construction runs another 4–6 months for a garage conversion. As a licensed general contractor, we manage plans, permits, and inspections from start to certificate of occupancy.

A well-built San Jose ADU rents for $2,400–$3,200/month in 2026 and adds significant resale value to the primary home. For most homeowners, a garage conversion pays itself back within 6–8 years — and unlocks flexibility for family, guests, or long-term rental income.